Hibernate三种实体映射，从建表到操作代码

映射关联大致分为三种 ：
一对一 ，一对多， 多对多
一.一对一

drop table if exists husband;create table husband(   id int not null  primary key ,   hname varchar(20) not null collate 'utf8_bin');drop table if exists wife;create table wife(   id int not null  primary key ,   wname varchar(20) not null collate 'utf8_bin',   constraint h_w_id foreign key(id)references husband(id))

package com.lyf.dao;import com.lyf.po.Hus;import com.lyf.po.Wif;import org.hibernate.HibernateException;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.Transaction;import org.hibernate.cfg.Configuration;import org.junit.Test;/** * Created by fangjiejie on 2017/4/16. */public class HusDao implements IHusDao{    private Configuration cfg=null;    private SessionFactory sf=null;    public HusDao() {        cfg=new Configuration().configure("hibernate.cfg.xml");        sf=cfg.buildSessionFactory();    }@Test    public void add() {        Session session=null;        Transaction tran=null;        try {            session=sf.openSession();            tran=session.getTransaction();            tran.begin();            Hus hus=new Hus();            hus.setId(3);            hus.sethName("hus2");            Wif wif=new Wif();            wif.setId(3);            wif.setwName("wif2");            wif.setHus(hus);            hus.setWif(wif);            session.save(hus);            tran.commit();        } catch (HibernateException e) {            tran.rollback();            e.printStackTrace();        } finally {            session.close();        }    }@Test    public void delete() {        Session session=sf.openSession();        Transaction tran=session.getTransaction();        tran.begin();         Hus h=session.load(Hus.class,3);         session.delete(h);        tran.commit();        session.close();    }@Test    public void update() {        Session session=sf.openSession();        Transaction tran=session.getTransaction();        tran.begin();        Hus h=session.load(Hus.class,1);        h.sethName("hus0");        h.getWif().setwName("wif0");        session.update(h);        tran.commit();        session.close();    }@Test    public void query() {        Session session=sf.openSession();        Hus h=session.load(Hus.class,1);        System.out.printf("Hus:%s Wife:%s",h.gethName(),h.getWif().getwName());        session.close();    }}

想要实现对主表操作，从表也跟着操作 可以设置hus实体

    @OneToOne(cascade = CascadeType.ALL)    @JoinColumn(name = "id", referencedColumnName = "id", nullable = false)    public Wif getWif() {        return wif;    }    public void setWif(Wif wif) {        this.wif = wif;    }}

二.一对多

drop table if exists father;create table father(   fid int not null  primary key ,   fname varchar(20) not null collate 'utf8_bin');drop table if exists son;create table son(   sid int not null  primary key ,   sname varchar(20) not null collate 'utf8_bin',   fid int not null,   constraint f_s_id foreign key(fid)references father(fid))

package com.lyf.dao;import com.lyf.po.Father;import com.lyf.po.Son;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.Transaction;import org.hibernate.cfg.Configuration;import org.junit.Test;import java.util.Iterator;import java.util.Set;/** * Created by fangjiejie on 2017/4/17. */public class FaterDal implements IFather{    private Configuration cfg=null;    private SessionFactory sf=null;    public FaterDal() {        cfg=new Configuration().configure("hibernate.cfg.xml");        sf=cfg.buildSessionFactory();    }@Test    public void add() {        Session session=sf.openSession();        Transaction tran=session.getTransaction();        tran.begin();    Father f1=new Father();    f1.setfId(7);    f1.setfName("f7");    Son s1=new Son();    s1.setsId(5);    s1.setsName("s5");    s1.setFather(f1);    Son s2=new Son();    s2.setsId(6);    s2.setsName("s6");    s2.setFather(f1);    f1.getSons().add(s1);    f1.getSons().add(s2);    session.save(f1);        tran.commit();        session.close();    }@Test    public void delete() {        Session session=sf.openSession();        Transaction tran=session.getTransaction();        tran.begin();        Father f=session.load(Father.class,7);        session.delete(f);        tran.commit();        session.close();    }    public void update() {    }@Test    public void query() {       Session session=sf.openSession();        Father f=session.load(Father.class,7);        Set<Son> sons=f.getSons();        Iterator<Son> it=sons.iterator();        while(it.hasNext()){            Son son=it.next();            System.out.println(son.getsName());        }    session.close();    }}

实现主表操作，连动从表，设置father实体类中

@OneToMany(mappedBy = "father",cascade = CascadeType.ALL)    public Set<Son> getSons() {        return sons;    }    public void setSons(Set<Son> sons) {        this.sons = sons;

三.多对多

drop table if exists teacher;create table teacher(   tid int not null  primary key ,   tname varchar(20) not null collate 'utf8_bin');drop table if exists student;create table student(   sid int not null  primary key ,   sname varchar(20) not null collate 'utf8_bin');create table teacherstudent(  tid int not null,  sid int not null,  primary key(tid,sid),  constraint t_s_1 foreign key(tid) references teacher(tid),  constraint t_s_2 foreign key(sid) references student(sid))

package com.lyf.dao;import com.lyf.po.Students;import com.lyf.po.Teachers;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.Transaction;import org.hibernate.cfg.Configuration;import org.junit.Test;/** * Created by fangjiejie on 2017/4/17. */public class StudentsDao implements IStudentsDao {    private Configuration cfg=null;    private SessionFactory sf=null;    public StudentsDao() {        cfg=new Configuration().configure("hibernate.cfg.xml");        sf=cfg.buildSessionFactory();    }@Test    public void add() {        Session session=sf.openSession();        Transaction tran=session.getTransaction();        tran.begin();        Teachers tea1=new Teachers();        tea1.settId(1);        tea1.settName("t1");        Teachers tea2=new Teachers();        tea2.settId(2);        tea2.settName("t2");        Students stu1=new Students();        stu1.setsId(1);        stu1.setsName("s1");        Students stu2=new Students();        stu2.setsId(2);        stu2.setsName("s2");        tea1.getStudents().add(stu1);        tea1.getStudents().add(stu2);        tea2.getStudents().add(stu1);        tea2.getStudents().add(stu2);        stu1.getTeachers().add(tea1);        stu1.getTeachers().add(tea2);        stu2.getTeachers().add(tea1);        stu2.getTeachers().add(tea2);        session.save(stu1);        session.save(stu2);        tran.commit();        session.close();    }@Test    public void delete() {        Session session=sf.openSession();        Transaction tran=session.getTransaction();        tran.begin();        Students s=session.load(Students.class,1);        session.delete(s);        tran.commit();        session.close();    }    public void update() {    }    public void query() {    }}

值得注意的是，如果在删除主表数据时，我们并不想，让从表数据一起删除。我们可以设置主表

 @ManyToMany(cascade = CascadeType.PERSIST)//增加连动，删除不联动    @JoinTable(name = "teastu", catalog = "bz", schema = "bz", joinColumns = @JoinColumn(name = "s_id", referencedColumnName = "s_id", nullable = false), inverseJoinColumns = @JoinColumn(name = "t_id", referencedColumnName = "t_id", nullable = false))    public Set<Teachers> getTeachers() {        return teachers;    }